In recent years, due to increase in awareness of energy saving, there have been proposed a large number of permanent magnet motors configured to use rare-earth permanent magnets having high coercivity in a rotator, to thereby realize high efficiency. However, the rare-earth permanent magnets are expensive, which leads to increase in cost of the electric motor. Therefore, in a rotator of a related-art general permanent magnet buried type electric motor, sintered ferrite magnets are used instead of the rare-earth permanent magnets. When the sintered ferrite magnets are used instead of the rare-earth permanent magnets as described above, the residual flux density, which represents the magnitude of the magnetic force, is reduced to about ⅓. In order to compensate for the lack of torque due to the reduction in magnetic force, it is necessary to form the permanent magnets into such shapes that surface areas thereof are increased as much as possible, thereby compensating for the lack of the magnetic force by the surface areas. Further, reluctance torque is actively used in addition to the torque caused by the permanent magnets. In this manner, the lack of the magnetic force due to the permanent magnets can be compensated for.
For example, the rotator of the permanent magnet buried type electric motor disclosed in Patent Literature 1 includes arc-shaped permanent magnets, a laminated core having punched holes for accommodating the permanent magnets therein, and a shaft. The punched holes are formed at a rate of one per pole. Further, the punched hole is formed into an arc shape that protrudes toward the rotator center.